Geothermal energy resources, power generation methods like vapour dominated, water dominated, flash steam, binary fluid and total flow concept of power generation

1. Geothermal Energy
By
Prof. Ashish Bandewar

2. Geothermal Energy
What is Geothermal Energy ?
It’s simply the heat energy of
the earth, generated by various
natural processes, such as:
1. heat from when the planet
formed and accreted, which has
not yet been lost (20%)
2.decay of radioactive
elements(80%).
3.friction

3. • Temperatures at the core–mantle boundary may
reach over 4000 °C
• The high temperature and pressure in Earth's
interior cause some rock to melt and solid mantle
to behave plastically, resulting in portions of
mantle convecting upward since it is lighter than
the surrounding rock. Rock and water is heated in
the crust, sometimes up to 370 °C

4. INDICATIONS
Reservoirs can be suspected in the areas where we
find :-
 Geyser
 Boiling mud pot
 Volcano
 Hot springs

5. EXPLORATION
 Bubbling mud, geysers and hot pools are good
indicators of geothermal activity at the surface, but
what is going on underground?
Exploration methods
 Areas are explored, analysed and mapped
 Geological, geophysical and geochemical data are
combined
 Field models are developed
 Geothermal potential is assessed
 Drilling sites are identified

6. SOURCES
 Hot water reservoirs
 Natural steam reservoirs
 Geo pressurised
reservoirs
 Normal geothermal
gradient
 Hot dry rocks
 Molten magma

7. Geothermal Reservoirs
• The rising hot water &
steam is trapped in
permeable & porous rocks
to form a geothermal
reservoir.
• Reservoirs can be
discovered by
 testing the soil
 analyzing underground
temperature

8. Extraction
• The heat energy can be brought to earth surface by
following ways..
 directly from hot springs/ geysers
 geothermal heat pump

9. BASIC METHODS AND TECHNOLOGIES

13. Dry Steam Plants: These were the first type of plants created.
They use underground steam to directly turn the turbines.

14. Flash Steam Plants: Most common plants. These systems pull deep, high
pressured hot water that reaches temperatures of 3600F or more to the
surface. This water is transported to low pressure chambers, and the resulting
steam drives the turbines. The remaining water and steam are then injected
back into the source from which they were taken..

15. Binary Cycle Plants: This system passes moderately hot geothermal
water past a liquid, usually an organic fluid, that has a lower boiling
point. The resulting steam from the organic liquid drives the turbines.
This process does not produce any emissions and the water
temperature needed for the water is lower than that needed in the
Flash Steam Plants (2500F – 3600F)..

17. Electricity Generation:

18. There are 3 types of power plants:-
 Dry steam power plant
 Flash steam power plant
 Binary cycle power plant

19. Dry Steam power plant

20.  The oldest type of Geothermal power plant used.
 Geothermal reservoir containing pure steam is
required.
 Pure dry steam drives turbine.
 Very rare type of geothermal power plant.
 Operating at California, Italy, and Japan.

21. Flash steam power plant

22.  Commonly used geothermal power plant.
 Geothermal reservoirs containing both hot water &
steam is required.
 Pressure changing system is required.
 Operating at Hawaii, Nevada, Utah & some other
places

23. Binary cycle power plant

24.  Does not use steam directly to spin turbines.
 Only the heat of the underground water is used.
 Vapourized hydrocarbons are used to spin the
turbine.
 Hydrocarbons having lower boiling point such as
isopentane, isobutane and propane can be used.
 No harmful gas is emitted to the atmosphere
because the underground water is never disclosed
to outside.
 This’s the worldwide accepted power plant.

25. Turbine & generator:-

26. Thermal efficiency of the plants
 It is low, around 7-10% because geothermal fluids
are at low temperatures compared to steam in
boilers.
 By the laws of thermodynamics this low
temperature limits the efficiency of heat engines in
extracting useful energy during the generation of
electricity.
 The efficiency of the system does not affect
operational costs as it would for a coal or other
fossil fuel plant, but it does factor into the viability
of the station.

27. Cost
 Direct use of geothermal energy is absolutely
cheaper than other energy sources.
 Cost of electricity generation depends upon certain
factors:
 Temperature and depth of resource
 Type of resource (steam, liquid, mix)
 Available volume of resource
 Size and technology of plant

28.  The initial investment is high.
 But after certain time period, the cost of electricity
becomes comparable to other resources of energy.
 US $0.05 to $0.08 (Rs. 2.772 to Rs. 4.4352) per
kWh

29. Geothermal Energy in India

30.  Geothermal provinces are estimated to produce
10,600 MW of power (experts are confident only to
the extent of 100 MW)
 Geothermal provinces in India: the Himalayas,
Sohana, West coast, Cambay, Son-Narmada-Tapi ,
Godavari, and Mahanadi
 Reykjavík Geothermal will assist Thermax to set up
a pilot project in Puga Valley, Ladakh (Jammu &
Kashmir)
 First operational commercial geothermal power
plant is likely to come up in AP with a capacity of
25 MW by Geosyndicate Pvt Ltd.

31. Advantages
 Available all the year around.
 Does not involve any combustion of fuel.
 Independent of weather
 Clean Resource – Very little emissions or overall
environmental impact.
 Economically Sound Alternative – The fuel is free,
rate / KWh likely to be competitive
 Overall, geothermal energy is a sustainable
resource.

32. Disadvantages
 Not widespread source of energy
 High installation costs
 Can run out of steam
 May release harmful gases
 Transportation
 Earthquakes

33. Conclusion
 Geothermal heating system can replace fossil fuel
heating system in a particular area.
 Annual costs for common heating purposes can be
reduced by more than 60%.
 Continued energy shortages have created added
interest in geothermal energy for power
generation.
 Geothermal energy appears to be a partial solution
to our energy needs.

34. EXTRA SLIDES